Anaplasmosis occurs in numerous mammal species such as humans, horses, dogs, cats deer, and ruminants and is caused by infection of granulocytic cells with the tick-borne agent Anaplasma phagocytophilum (“Aph”) (formerly known as Ehrlichia equi). Frequently reported clinical signs in granulocytic ehrlichiosis in humans are leukopenia and thrombocytopenia. Common clinical signs in dogs are fever, thrombocytopenia, swelling of the lymph nodes, and anorexia.
Anaplasma platys (“Apl”) (formerly known as Ehrlichia platys) is another agent that is likely transmitted through ticks such as Rhipicephalus sanguineus or other arthropod. A. platys may be co-transmitted by a tick with Ehrlichia canis. A. platys can cause infectious canine cyclic thrombocytopenia (ICCT), but infected dogs are usually asymptomatic. A. platys infection is difficult to detect in vivo because the numbers of the bacteria in the blood are usually low. Serologic tests for Apl can be inaccurate because of cross-reactivity with other Anaplasma sp.
Tickborne infectious disease caused by A. phagocytophilum in human and dogs is a serious problem, whereas A. platys infection is presently considered to be of minor importance. Current serodiagnostic tools for A. phagocytophilum can not differentiate the two infections. Methods of detecting Aph and Apl and methods of differentiating between the two infections are needed in the art.
The onset of clinical symptoms occurs during the acute phase of anaplasmosis—typically within 7 to 14 days post infection—and can precede the advent of measurable levels of antibodies against some Aph antigens. Thus, there is a need for a rapid, sensitive and reliable immunological test for Aph infection in mammals exhibiting clinical symptoms of acute anaplasmosis.